The budget is ultimately limited by the government's ability to extract value. There are no similar limits to the quantity of laws and regulations that can be in effect at the same time. Legislators can of course impose an arbitrary limit, but they can just as easily increase the limit or repeal it, if they don't like it.
The number of laws is limited by several factors, among them:
For instance, when the rule of avoidance in late imperial China created a 5x increase in rate of new regulations, the result was up to 30% decrease in tax collections and a counterintuitive increase in the power and influence of local clerks, gentry and militias, laying the groundwork supportive of the eventual mutiny against and collapse of Qing rule